Vitamin D regulates the body’s calcium and phosphorus levels to maintain strong bones and teeth. It also helps immune system function. This vitamin can be obtained through the diet but is also synthesized by the skin after exposure to sunlight. Given Canada’s long, darker winter months, it’s important that adults get sufficient vitamin D through diet or supplementation during the winter. Adults need at least 200 IU per day, while those over age 50 require between 400 and 600 IU.

At the University of Wisconsin, researchers studied the role of vitamin D in the body. They found that both too much or too little vitamin D negatively impacts immunity, while the right amount can help suppress type I diabetes, rheumatoid arthritis and inflammatory bowel disease. They also found the action of vitamin D could suppress inflammatory T-cell activity and concluded there may be a role for vitamin D in the treatment of autoimmune disorders.

In another study closer to home, researchers from Mount Sinai Hospital in Toronto discovered that young Canadian women were prone to vitamin D deficiencies despite dietary precautions. They observed 796 women, aged 18-35 years, for one year. While the women’s vitamin D levels were monitored, they were asked not to make any significant diet or lifestyle changes. Results indicated that despite getting vitamin D in the diet, 26% of young women still had low vitamin D levels. Apart from considering supplementation, experts recommend that we expose our faces and hands to sunlight (during non-peak times) in the winter months for 15 minutes each day.

Sources: FASEB J 2001 Dec;15(14):2579-85; Eur J Clin Nutr 2001 Dec;55(12):1091-7; Leslie Beck’s Nutrition Encyclopedia by L Beck, Prentice Hall:2001